The older Stereomour uses fixed bias - the only adjustments are the two hum balance controls. Center them approximately to start, then adjust each channel for minimum hum.
Manuals are available, which include instructions for voltage checks to confirm correct operation. If you post a few photos, we can identify the version more precisely so you get the right manual. Since many customers make modifications, we can also identify whether changes have been made, at least in most cases.
